a) Field of the Invention
This invention relates to a gas generating device for actuating an apparatus such as an air bag system or a webbing pretensioner of a seat belt system, for example, in the event of a collision of an automotive vehicle. More specifically, this invention is concerned with a gas generating device equipped with a hammer pin trigger device which causes a hammer pin to strike a detonator of a gas generator.
b) Description of the Related Art
An air bag system and/or a webbing pretensioner has been used to protect an occupant in the event of a collision of an automotive vehicle. It is necessary to make these devices actuate instantaneously at the time of a collision, so that a gas generating device is employed to cause explosive combustion of a gas-generating chemical reagent such as explosive for the generation of high-temperature gas.
These gas generating devices are available in types, one being electrically fired and the other mechanically fired. Mechanical devices are however finding increasing popularity in recent years for their simpler construction and lower price.
Referring first to FIGS. 8 through 10, a description will hereinafter be made of a conventional mechanically-triggered gas generating device as applied to a pretensioner of a webbing retractor in an automotive seat belt system.
FIG. 8 is a front view of the webbing retractor equipped with the pretensioner, FIG. 9 is a partly cross-sectional view of the mechanically-triggered gas generating device, and FIG. 10 is a side view of the webbing retractor and shows directions of gas blown out of the mechanically-triggered gas generating device.
The webbing retractor will first be described. As is illustrated in FIGS. 8 and 10, the webbing retractor 1 comprises a frame 2 made of a steel plate, having an inverted square-U-shaped configuration in cross-section and mutually-opposing side walls 2a,2b, a take-up reel 3 rotatably supported at opposite ends thereof on the side walls 2a,2b and adapted to wind in or take up a webbing 4, a winder unit 6 for normally biasing the take-up reel 3 in a webbing-winding direction, and an emergency lock mechanism 5 for locking rotation of the take-up reel 3 to prevent any further release of the webbing 4 upon occurrence of an abrupt deceleration on an automotive vehicle on which the webbing retractor 1 is mounted.
The webbing retractor 1 is mounted on a vehicle body by a tongue-shaped mounting member 7 disposed on a lower side of the frame 2 as viewed in the drawings. The webbing 4, which is made of polyester fibers, can be wound out or released in an upward direction as viewed in the figures while being guided by a webbing guide 8. Attached as an integral unitary member to an upper end portion of the side wall 2a of the frame 2 by way of a horizontal connecting portion is a plate-shaped mounting bracket 2c for the gas generating device. This mounting bracket 2c extends in parallel with the side wall 2a. On opposite sides of the mounting bracket 2c, a hammer pin trigger device 20 and a pretensioner 10 are mounted, respectively, so that the hammer pin trigger device 20 and the pretensioner 10 are arranged opposite each other. The hammer pin trigger device 20 and the pretensioner 10 are threadedly secured on the mounting bracket 2c by bolts 26, whereby the bracket 2c is located between the hammer pin trigger device 20 and the pretensioner 10.
As is illustrated in FIGS. 9 and 10, the hammer pin trigger device 20 has a housing 21 mounted on one side wall 2e of the mounting bracket 2c. This housing 21 has a bottom-closed cylindrical configuration. On an open-end-side outer peripheral wall of the housing 21, mounting flanges 21a,21b are disposed so that they extend perpendicularly to an axis of the housing 21. A hammer pin guide member 25, which will be described subsequently herein, is fitted in the open end of the housing 21, so that the housing 21 is closed.
In the housing 21, a rod-shaped hammer pin 24 is arranged slidably in the direction of the axis. A tip portion of the hammer pin 24 is pointed and is inserted in an aperture 25d of the hammer pin guide member 25. The hammer pin 24 is therefore axially displaceable within the housing 21.
The pretensioner 10 has a cylindrical housing 11 mounted on an opposite side wall 2f of the bracket 2c and a cylinder 12 threadedly fitted in a free end portion of the housing 11. The pretensioner 10 therefore has an L-shaped configuration as viewed in front elevation.
Accommodated in the housing 11 is a gas generator 30 which is disposed in contact with the side wall 2f of the mounting bracket 2c.
This gas generator 30 comprises, as depicted in FIG. 9, a gas-generating chemical reagent 32 enclosed within a bottom-closed cylindrical casing, a detonator holder 34 sealing the gas-generating chemical reagent 32 and holding a detonator 33 on an axis, and a cap 35 defining a hammer pin guide aperture 35a for guiding the tip portion of the hammer pin 24. The detonator 33 is in the form of a detonator which is fired when struck by the pointed tip portion of the hammer pin 24, and is disposed opposite the hammer pin guide aperture 35a. The detonator holder 35 also defines a through-hole 34a so that when the detonator 33 is fired by the hammer pin 24, resulting flame is allowed to blow out into the gas-generating chemical reagent 32 to ignite the gas-generating chemical reagent 32.
Operations of the above-described hammer pin trigger device 20 and the gas generator 30 will next be described.
When an abrupt inertia of at least a predetermined value acts on an unillustrated inertia body arranged in the hammer pin trigger device 20 as a result of a collision or the like of the automotive vehicle, the inertia body is caused to move axially against magnetic repulsion between the inertia body and a cylindrical magnet (not shown). As a result, the hammer pin 24 is caused to move toward the gas generator 30 so that the pointed end portion of the hammer pin 24 strikes and fires the detonator 33. The gas-generating chemical reagent 32 ignited as a result of the firing of the detonator 33 generates a great deal of high-temperature gas G. This high-temperature gas G breaks up the bottom of the casing 31 and blows out into a gas compartment 13 of the pretensioner 10. As a consequence, a piston 15 disposed within the cylinder 12 of the pretensioner 10 is driven by gas pressure P so that the piston 15 is caused to move within the cylinder 12. A wire cable 16 connected to the piston 15 is therefore pulled by pulling force F. Accordingly, the take-up reel 3 on which the wire cable 16 is wound is biased in a direction to wind up the webbing 4, whereby webbing slack is taken up. The occupant's body is therefore firmed restrained on the seat by the slack-free webbing 4, thereby reducing the distance of a sway toward the front of the vehicle body due to an impact of a collision and hence protecting the occupant from injuries which would otherwise occur as a result of impacting a steering wheel or the like.
The above-described gas generator 30 is accommodated within the housing 11 so that the gas generator 30 is located opposite the side wall 2f of the mounting bracket 2c. Further, the cap 35 defines the hammer pin guide aperture 35a through which the hammer pin 24 extends. As a consequence, a part of high-temperature and high-pressure gas G generated by the chemical reagent 32 flows backward and blows out through gaps between the gas generator 30 and housing 11 and the side wall 2f of the mounting bracket 2c. The mounting bracket 2c is also provided with the through-bore 2d through which the hammer pin 24 extends. The high-temperature and high-pressure gas G which has passed through the through-bore 2d blows out through a gap between the impact pin trigger device 20 and the side wall 2e of the mounting bracket 2c. Since the gas so blown out has a considerably high temperature, it may give unfavorable thermal influence to components arranged around the pretensioner 10 and the hammer pin trigger device 20.
This potential problem is not limited to the above-described webbing retractor but also exists in the case of an air bag arranged inside the steering wheel or at another location as long as its gas generating device or the like is mounted in a similar manner.